Laundry optimization problem

The facts:
I have two mobile stands for laundry hanging, both occupy the same floor space. The difference is that one of them has half the number of clothesline wires (denoted hereafter as "the sparse stand").
Another fact is that I prefer avoiding clothes clips, because they leave marks. This means that I hang shirts, for example, by folding them by their armpits.

The optimization goal:
Having the laundry dry as fast as possible. The exact optimization goal is not the makespan (the time difference between hanging the first item and removing the last) but rather the free clothesline wires. To be even more precise, the time in which there is enough free clothesline wire length to hang another washing machine (this is weekend washing - lots of accumulated laundry or once-a-week machine loads). This is a micro-goal which should lead to high laundry throughput during the weekend.

The free parameters:
I can choose where to hang laundry by the length of the items. Hanging long items on the sparse stand, short items on the dense stand, will bring to an even distribution of moist in the air, because the long items contain more moist, but the sparse stand has less wires, so the moist division is more or less even. This may lead to many items drying together.

I can choose, on the other hand, to hang the long items on the dense stand. Long items can carry their weight without clips even when they are not balanced over the wire (e.g., a large shirt hanging by armpits). Short items must be hanged by their middle. Folding the small items in half creates a high density of moist in the upper part of the dense stand, and the air flow is impeded. the small items can hang on the sparse stand without touching one another, while the long items touch one another only a little, even on the dense stand.
  • Current Mood
    contemplative contemplative

הילדה הכי יפה בגן

זאב ראה DVD של שירי ילדים, עם השיר "הילדה הכי יפה בגן". על המרקע ביצעה ילדה נחמדה כבת חמש פנטומימה. הוא הצביע בנחישות על המסך ואמר "יעלי". לא הצלחתי לשכנע אותו אחרת.

xfig figures for an IEEE paper

It is amazing that I spent a whole day on this. There are two things to do to Xfig, to make it export figures properly for IEEE Xplore, that is with embedded and subset fonts.  The first can be done before exporting, but the second needs to be done before drawing, or you will need to change properties of single items.

Use Latex fonts: Choose Text. on the bottom right of xfig, click on the font name, and choose Latex fonts. Choose any of them. 
Then, in the "text flags" menu, where it says "hidden=off", click and choose for the "special flag" option the value "special" and not "normal". (Is this like double negative? what is a normal special flag? what is a special special flag? what is a flag that is called special flag? a special flag flag?)

Then you can export an existing figure, there is no need to write text again. But you will need to export all your figures again.

The other thing is use "filled" instead of "pattern" in thick lines and shape filling. It may look the same, but it will prevent  a type 3 font. This you need to do either before you draw, or after - choose edit and click on all the filled shapes, apply and done.

Amazon Update

It seems like Amazon changed their reserve price algorithm last July, using a non-symmetric algorithm instead of the AR(1) up-down symmetric algorithm, and changing floor and ceiling values. Then in October it seems like they returned to using a simple constant minimal price algorithm, with yet a new level of a minimal price!

Was our paper a reason for the abandoning of the (no longer) hidden dynamic reserve price?

Deconstructing Amazon EC2 Spot Instance Pricing

Everybody looks at Amazon's price traces, zooming in and out, averaging them. Most of the time, people look at the graphs, and assume that this is naturally how it should be: a noisy line. After all, why should anything change? The anchor (the on-demand price) stays the same, after all.

But what if you look at the price, compared with the fraction of the time in which it was possible to get an instance for this price? We call this the availability of the price. Then some funny patterns show. Beautiful Straight lines. The patterns become even funnier, when the prices are normalized by the on-demand price, so they are all on the same scale. Then all the supposedly market-driven prices form graphs which fall exactly one on top of the other. That is, for all regions but one. What is so special about US-east? And, for Linux. Windows instances have price groups. Do market rules work differently when instances run Linux?

More funny features are changes in the floor price, or in the often visited highest price, which were coordinated across different continents and instance types. As far as I stretch my imagination, I cannot believe this to be the result of market forces.

If prices are not set by market forces, they are artificially set, although Amazon claim the prices are market driven. If prices are artificial, clients should not look for market effects in the prices. For example, the often visited band of prices, above which we hardly ever see prices, is not market driven. Rises in the price do not necessarily say anything about supply and demand, nor do low prices. These are all the result of an algorithm we are told little about.

If prices are the result of a secret algorithm, then pricing methods are subject to quick and unforeseen qualitative changes. In particular, it seems like Amazon update their algorithms every 6 months. Sometimes they announce the change (December 2009, July 2011), and sometimes they don't (Jan and Feb 2011, Feb 2010). So clients, watch out during January 2012 - you might be surprised then.

If the algorithm Amazon use is artificial, it should be possible to deconstruct it. In our recent study, we present a model which accurately mimics the EC2 pricing algorithm. Our model shows that EC2 traces are consistent with Amazon using a dynamic hidden reserve price. That is, Amazon uses a random method (a truncated auto-regressive process) to determine the next reserve price: a price below which no instances are granted, even if it means Amazon's computers will remain unused. If you want to read more, see our finding in Technion
CS Tech report number CS-2011-09

שרות קריסטל

לפני חודש היתה לי תקרית לא נעימה עם טכנאי של שרות קריסטל. הטכנאי נתן לי התראה רק של רבע שעה במקום חצי שעה, ואז כעס כשרק המטפלת הכניסה אותו ולא אני. חמש דקות אחר כך הוא ביקש אישור להחליף חלק יקר בטלפון, או שהוא הולך. לאחר שהגעתי והעבודה הסתיימה, רצה לחייב אותי בעלות של שני חלקים. סרבתי לשלם על החלק הנוסף שלא נתתי אישור להתקנתו, והוא התלונן שהובטח לו שיהיה גבר בבית, והנה - אשה. כמובן שכל השיחה הגיעה לטונים גבוהים מאד.

כעת שרות קריסטל מציעים לי "לחדש" את הביטוח על המכשיר, בייחוד לאור התקלה. לא שאי פעם עשיתי ביטוח - ביטוח מכשירי חשמל זו זריקת כסף של שונאי סיכון. ואוהבי התעללות טכנאים. בכל מקרה, כשהסברתי לנציגה שאני לא מבטחת בחברה בה הטכנאים צועקים עלי, היא הציעה שתעביר אותי לשרות הלקוחות, שם אוכל להתלונן על היחס של הטכנאי. הסכמתי. הועברתי. המתנתי. הסברתי.

נציגת שרות הלקוחות הודיעה לי שאני יכולה לשלוח פקס או להגיע לסניף, אבל הם לא יכולים לטפל במקרה טלפונית, כי הטכנאי ודאי לא יזכור את הארוע. ונשאלת השאלה, אם אטרח לרשום את כל הסיפור, האם הטכנאי ייזכר?

על גאווה ודעה קדומה

על: אמא, את יכולה לנשק חברה על הפה?
יעל:אז למה את מנשקת רק את אבא על הפה?
אני: גם את האחיות שלי ואמא שלי אני לא מנשקת על הפה, נשיקה על הפה שמורה לבן זוג. יש נשים שיש להן חברה שהיא בת הזוג שלהן, אבל לי יש את אבא.

יעל: למה אנשים שהם מכוערים אז אנשים אחרים חושבים שהם רעים והם לא רעים?
.אני חסרת הסברים. התניות? נוח לנו להאמין כך? השארתי ילדה תלויה באוויר


יעל רצתה לדעת -אם לא מדברים עם זרים, איך מכירים חברים חדשים?
הלואי והתשובה לכל הכרות אינטרנט היתה פשוטה כמו תשובה לילדה בת ארבע וחצי.